Which distances are available
The calculator offers four fixed distances plus a custom one: Sprint (750 m swim, 20 km bike, 5 km run), Olympic (1.5 km, 40 km, 10 km), 70.3 half distance (1.9 km, 90 km, 21.1 km) and full distance (3.8 km, 180 km, 42.2 km). These figures come from the official IRONMAN distance overview, see sources.
How it is calculated
Swim time = swim distance in metres divided by 100, times your pace per 100 m. Bike time = bike distance in kilometres divided by your speed in km/h, times 3600 seconds. Run time = run distance in kilometres times your run pace per kilometre. Total time = swim time + T1 + bike time + T2 + run time.
In "Set a target time" mode the last formula runs in reverse: run pace = (target time − swim time − T1 − bike time − T2) divided by the run distance in kilometres. Enter a start time and the table also shows the clock time at each transition.
Context and limits
The calculator assumes an even pace in each discipline, without stops, aid stations or headwind swings. Real race times differ, especially on the bike due to elevation and wind, and on the run due to heat and fatigue after cycling. T1 and T2 depend heavily on the venue, from a few seconds to several minutes on long transition walks.
The 70.3 distance is named after its total length in miles, 1.2 + 56 + 13.1 miles, equal to 1.9 + 90 + 21.1 kilometres. The full distance is likewise named after 140.6 miles.
Worked example
For the 70.3 half distance with a 2:00 min/100 m swim pace, 30 km/h on the bike and 5:30 min/km run pace, with 2:00 min T1 and 1:30 min T2: swim 38:00 min, bike 3:00:00 hours, run 1:56:02 hours. Together with the transitions, that totals 5:37:32 hours.
If you instead want to finish in 5:30:00 hours, with the same swim, bike and transitions, the "Set a target time" mode shows the required run pace of about 5:09 min/km.
Frequently asked questions
What distances make up a sprint triathlon?
750 m swim, 20 km bike and 5 km run, according to the official IRONMAN distance overview.
How long is the 70.3 half distance?
1.9 km swim, 90 km bike and 21.1 km run, totalling 113.1 km or 70.3 miles, hence the name.
How long is the full distance?
3.8 km swim, 180 km bike and 42.2 km run (a full marathon), totalling 226.3 km or 140.6 miles.
How do I work out the run pace for a target time?
Subtract swim time, T1, bike time and T2 from the target time, then divide the remainder by the run distance in kilometres. At a 5:30:00 target, 38:00 min swim, 3:00:00 bike and 3:30 min transitions on the 70.3 distance, that comes to about 5:09 min/km.
Does the calculator show clock times too?
Yes, once you enter a start time in hh:mm format, the table shows the clock time at the end of each segment alongside its duration.